Formation of Polymer–Ionic Liquid Gels Using Vapor Phase Precursors

We studied a new method for preparing polymer–ionic liquid (IL) gels via deposition of vapor phase precursors onto thin layers of IL. The solubility of 2-hydroxyethyl methacrylate in 1-ethyl-3-methylimidazolium tetrafluoroborate enabled polymerization at both the IL–vapor interface and within the IL layer. We observed a transition from a viscous liquid to a gel with increasing polymer concentration. At short deposition times, there were two distinct molecular weights reflecting polymerization at the IL–vapor interface and within the IL layer, while at longer deposition times the molecular weight distribution within the IL layer broadened. The polymer chains within the IL were orders of magnitude larger than the polymer chains at the IL–vapor interface, and increasing the reactor pressure was shown to increase the molecular weight. Our ability to form high molecular weight polymer chains allows for the formation of gels for utilization as fuel-cell membranes and thin-film transistors.